1. Field of the Invention
The present invention relates to bulk material unloading systems for ships generally and, more particularly, but not by way of limitation, to a novel conveyor system for unloading bulk cargo from ships, which conveyor system has significant advantages over conventional conveyor systems for unloading bulk material from ships.
2. Background Art
Bulk cargo ships are widely used for conveying a large range of bulk materials, such as iron ore, coal, grain, woodpulp, and gypsum, for example. Until recent developments in unloading systems, such materials were unloaded using buckets suspended from cranes located on the ship or on shore adjacent the ship.
In recent years, self unloading systems have been developed which use conveyors installed on the ships under hopper holds which contain the bulk material. In a typical such system, a plurality of holds are arranged fore and aft, each hold having a plurality of hoppers formed at the bottom of each, the hoppers having discharge gates at the apexes thereof for the controlled discharge therethrough of the bulk material. The discharge gates are arranged in two fore and aft lines, the lines being disposed generally midway between the centerline of the ship and the sides of the hull. Two parallel conveyors are provided under the lines of discharge gates, extending from the aft discharge gate in the aftermost hold to the forward gate in the forwardmost hold. At the latter point, the parallel conveyors discharge the bulk material onto two cross conveyors which discharge onto the lower end of a straight, inclined conveyor which, in turn, raises the bulk material to the deck of the ship. On the deck of the ship, the bulk material is discharged onto a boom-mounted conveyor to tranport the bulk material over the side of the ship to another vessel or to a point on land.
There are a number of disadvantages to the conventional system described above. The narrowing of the forwardmost hold adds complexity in the converging of the parallel conveyors to the cross conveyors. This complexity increases the amount of spillage of the bulk material. The straight inclined conveyor decreases the volume of the forwardmost hold that would be otherwise available for the bulk material. The latter problem results in less stability for the ship, due to the concomitant raising of the center of gravity, which must be compensated for by adding ballast.
Accordingly, it is a principal object of the present invention to provide an improved bulk material conveyor unloading system for a ship, which system maximizes the quantity of bulk material that can be carried by the ship.
It is an additional object of the invention to provide such an improved unloading system which is simpler and more economical to install than conventional unloading systems.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.